Pick a new Hero.
Note that your choice of new Hero is restricted to one of four that the game presents to you, so you might not get the one you want. These four Heroes can (as of 0.63.4) be any Heroes except those in use by other players in the game. (Prior to 0.63.4, the Hero options were selected in the same way as those for the strt of the game, with a Starter Hero in slot 1).
If you’re playing as Loki then, once you reach Level 6, he’s bound to cast this spell at some point. So be prepared.
Game Update History
0.63.4, October 2021: Hero selection mechanism changed